Methods and apparatus for suppressing jet noise



METHODS AND APPARATUS FOR SUPPRESSING JET NOISE Filed Oct. 10, 1960 April 3, 1962 s. P. MAYTNER 3 Sheets-Sheet 1 INVENTOR. STEPHEN P. MAY TN ER ATTO RNEY April 3, 1962 s. P. MAYTNER METHODS AND APPARATUS FOR SUPPRESSING JET NOISE Filed Oct. 10, 1960 5 Sheets-Sheet 2 FIG. 2

INVENTOR. P. MAY T N E R STEPHEN ATTORNEY April 3, 1962 s. P. MAY.TNER

METHODS AND APPARATUS FOR SUPPRESSING JET NOISE Filed 001;. 10, 1960 3 Sheets-Sheet 3 om m3 INVENTOR.

STEPHEN P. MAY TNER ATTORNEY United States Patent 3,027,710 METHODS AND APPARATUS FOR SUPPRESSING JET NOISE Stephen P. Maytner, 356 William St., East Orange, NJ. Filed Oct. 10, 1960, Ser. No. 61,525 13 Claims. (Cl. 60-356) This invention relates in general to jet propulsion plants for transportation vehicles, such as aircraft, and has particular reference to apparatus coupled with plants of this class to reduce the noise of the jet blast as it affects persons in the vicinity.

Prior to this invention, others have proposed various devices and mechanisms for suppressing jet noise. One of such proposals is to be found in the complicated mechanism disclosed in the recently issued US. Patent to Tyler et a1. 2,931,171 of April 5, 1960, and characterized by a combination of a. large number of movable parts, which together represent an assembly of considerable weight.

An object of the present invention is to provide a novel noise suppressor for jet propulsion engines in particular.

Another object of this invention is to provide a relatively simple noise suppressor substantially free of moving parts which may be readily coupled with a jet propulsion plant.

Still another object of the present invention is to provide a novel and unique apparatus which, when coupled with a jet propulsion plant, suppresses or reduces the noise created thereby and also imparts useful power thereto.

Still another object of this invention is to provide a novel and unique apparatus which is substantially free of moving parts and which, when coupled with a jetpropulsion plant of an airplane, reduces or suppresses the noise created thereby, modifies the temperature of the exhaust nozzle thereof, and also imparts useful power thereto in the course of said airplane in flight.

These as well as other objects and advantages of the present invention, will in part be explained and otherwise in part will be apparent to those skilled in the art to which the present invention pertains as the following specific description is read in connection with the accompanying drawings, wherein:

FIG. 1 is a foreshortened view in perspective of a jet propulsion plant in combination with a novel embodiment of the present invention, a part being broken away to show part of the interior construction of said embodiment.

2 is an enlarged end view looking towards the normally downstream end of the novel combination taken on line 2-2 of FIG. in the direction of the arrows.

FIG. 3 is an enlarged cross sectional view taken on line 3-3 of FIG. 5 looking in the direction of the arrows.

FIG. 4 is an enlarged cross sectional view taken on line 4-4 of FIG. 5, but with all parts omitted except the inlet part of the funnel and jet-propulsion housing and the H supporting spacers.

FIG. 5 is a reduced-scale view of the apparatus in FIG. 1, with the jet-propulsion plant being shown in side elevation and the novel noise-suppressing apparatus combined therewith at the downstream or exhaust end thereof'being in vertical axial section, and partially broken away.

As shown in the drawings the jet propulsion plant comprises a housing 11 in which is contained a propulsion jet engine which may be of any of the conventional types known to the art as jet, turbojet or turboprop engines, in one type of which air is taken in through the opening at the forward end 12, travels into compressors for compressing same, and then is fed into a fuel chamber wherein combustion takes place and the hot expanding gases so created jet out through the open tail pipe or downstream end 13 under greatly increased pressure and speed. Said jet propulsion plant 10 may be coupled to an airplane (not shown) in any manner well known to the art. In general one or more pairs of said jet propulsion plants 10 are mounted on the Wings of an airplane in the manner well known to the art.

According to the present invention, I provide a novel unitary noise-suppression and thrust booster assembly 20 which, as shown in FIGS. 1 andS, is coupled with a jet propulsion plant 10 of an airplane (not shown). Said unitary assembly 20 comprises a somewhat tubular or hollow element 21 which as shown is broadly of funnel shape, with a restriction at the throat thereof. In the illustrative embodiment of my invention, as shown in FIGS. 1 and 5, the inlet portion of the funnel 21 is a hollow inlet tube 22 of gradually decreasing internal diameter as well as external diameter from the front extremity 23 to the rear extremity thereof. The front extremity 23 may be in the form of a lip which may be a narrow internally extending head or flange as shown in FIG. 5. However, if desired, the lip, which is located at theleading edge of the funnel 21 for restricting the inlet passageway for air, may be omitted. Secured to or integral with the rear extremity of the inlet 22 is an outwardly extending annular flange 28. An outlet tube 34) of the funnel 21 is coupled with said inlet tube 22 by welding or in any other convenient manner to make airtight hermetic seal therewith. As shown in FIG. 5, the outlet tube 39 is so disposed that its center-line is in alignment with the center-line of the inlet tube 22, and the forward edge of said outlet tube 3% is located forwardly of the rear extremity of inlet tube 22 and flange 28. The outer edge of flange 28 is welded or otherwise coupled to the inner surface of outlet tube 30 to make air-tight, hermetic seal therewith. With the outlet tube 30 so disposed and rigidly connected to the inlet tube 22 and flange 28, there is provided the funnel 21 having an inwardly extending annular collar 32 providing a constricted throat defining a constricted passageway between the hollow inlet tube 22 and the outlet tube 30. Integral with the outlet tube 30 and extending outwardly therefrom is an apron reflector or deflector 33 which extends a considerable distance rearwardly of the outlet tube 30 and is an extension of the lower portion of outlet tube 30 over an arc thereof preferably in the range of about 30-180.

When in combination with a jet propulsion plant 10, secured to an airplane (not shown) to provide the driving force therefor, in an illustrative embodiment of the inventi-on, the assembly 20 is coupled therewith as shown in FIGS. 1 and 5. As shown in said illustrative embodiment, illustrated in FIGS. 1 and 5, the rear, tail or downstream end of the housing 11, out of the rear extremity of which the hot gases from the jet propulsion plant 10 normally discharge into the atmosphere, is located in the inlet tube 22. The inlet tube 22, which extends forwardly of said rear extremity of housing 11, is

' connected to said housing and is maintained in spaced relationship therefrom by a plurality of, such as the four shown, longitudinally elongated supports 34 of H-shaped cross-section spaced apart and rigidly secured to the downstream end of the housing 11 and to the inlet tube 22 by welding, rivets, or in any other desired and convenient manner. Referring to FIG. 5 the inlet tube 22 is so carried by the housing 11 and is of such dimensions and contour that preferably the portion thereof surrounding the rear end of the housing 11 is in general geometrically similar thereto and the remainder rearwardly thereof is of gradually decreasing diameter. In the combination as shown, the funnel 21 is so disposed relative tothe housing 11 that its longitudinal center-line is approximately in alignment with the longitudinal center-line of the housing 11 and the throat 32 carried bythe funnel 21 is located rearwardly of the rear, tail or downstream terminal of the housing 11. With such relationship, in the course of airplane travel motivated by operation of the jet propulsion plant 10, four quarter-annular streams of air, pass between the inlet tube 22 and the downstream end of the housing 11. One of the functions of said streams travelling in a direction opposite to the direction of travel of plant 10, is to serve to cool the downstream end of the housing 11 out of whose downstream extremity occurs discharge into the atmosphere of the hot gases from the propulsion plant 10. In addition, said four quarter-annular streams unite at the rear extremity of the housing 11, to become an annular air collar around said hot gases discharging out of the rear extremity of said housing 11. Due to the fact that the remainder of the inlet tube 22 and the throat 32 are of decreasing diameter in the direction of travel of said annular collar of air around said discharging hot gases, there is appreciable intermingling of 'the hot gases and air and also a compression of said components at least until they reach the discharge terminus of the throat 32 and then expand to impart a forward thrust in the direction of travel of said plant 10.

Mounted in the outlet tube 30 is a gas deflection subassembly comprising an elongated central hollow or tubular core element 35 whose external diameter is considerably less than that of the outlet tube 30 and whose leading or forward end terminates in a cone 36 which has as one of its functions to act as a spreader of the hot gases as they are discharged out of the tail or downstream end of the housing 11. The tubular core element 35 is disposed centrally in the opening through outlet tube 30 and preferably extends therethrough, with the forward end 36 thereof extending forwardly beyond the throat 32. The rear end of tubular core element 35 is located rearwardly beyond the rear end of outlet tube 3!) but forwardly of the rear extremity of the apron 33. The front extremity of the spreader cone 36 is preferably located adjacent the rear extremity of the housing 11 and may be disposed either inside of said outer extremity as shown in FIG. 5, in the plane of said outer extremity or a short distance rearwardly beyond said outer extremity (not shown). In any case the peak of the spreader cone 36 is preferably disposed approximately on the common longitudinal center-line extending through said housing 11 funnel 21 and tubular core element 35. Besides acting to spread the core of hot gases into annular shape, tubular core element 35 also serves to compress them in their normal course of travel thereby. Mounted on tubular core element 35 and supporting said tubular core element 35 in central position relative to the funnel 21 are a plurality of like elongated hollow tubes or stream-dividing members 40, which in the illustrative embodiment of the invention as shown in the drawings, are eight in number, are preferably spaced equi-distant from each other and therefore are 45 apart. Said stream-dividing members 40 are secured to said tubular core element 35 and extend lengthwise along the length thereof and extend radially and outwardly therefrom. Each of said stream-dividing members 40 comprises a pair of like elongated plates 41, with the corresponding edges 43 of the corresponding elongated ends thereof being secured together by welding or in any other convenient manner to provide an air tight, hermetic seal. Said plates 41 so secured together preferably extend outwardly and away from each other from said edges 43 secured together. Thus in a width-wise direc tion, the plates 41 in vertical cross section are in the form of a V. The plates 41 are also preferably arranged relative to each other so that they extend outwardly and away from each other along the length thereof. The outer edges of the plates 41, which are in divergent relationship with respect to each other in both their circumferential and axial directions, are covered by an arcuate portion 42 integral therewith or with a cover-plate (not shown) if desired to make an air-tight and hermetic seal therewith. The leading end of the upper edges of the plates 41 is also partially covered with the forward part of the arcuate portion 42 so that the height of the tear drop shaped opening 44 at the leading edge of each stream-dividing member 40 is considerably less than the tear drop shaped opening 45 at the trailing edge of stream-dividing member 40. The trailing edge 46 of each stream-dividing member 40 is preferably in a plane at approximately right angles to the length thereof; and the leading edge 47 of each stream-dividing member 40 is preferably at an ob tuse angle to the length thereof and may be arcuate and preferably convex as shown. Each of said stream-dividing members 40 is mounted on the tubular core element 35, with the edges thereof located on a line on the outside surface of said tubular core member 35 and parallel to the center-line thereof so that the stream-dividing member 40 is disposed approximately radially thereon. In such position, with the trailing edge 46 thereof being flush with the trailing edge of tubular core element 35 and extending rearwardly of the rear edge of outlet tube 36, with the leading edge 47 defining the opening 44 located fOIE wardly of the throat 32, with'the cover 42 hearing against the inside surface of tube 30 and with the forward edge of the cover 42 being in contact with that portion of throat 32 which is of smallest diameter, each stream-dividing member 40 is secured by welding or in any other manner along its entire edges 43 to tubular core element 35, along its entire annular forward edge to the throat 32 to make air seal therewith around the entire circumference of that portion of said throat of smallest diameter and also along the outer face of cover 42 in contact with outlet tube 30.

In such construction, I have provided a plurality of substantially or approximately radially disposed elongated stream-dividing members 40, which due to the lead opening 44 being of preferably tear drop shape geometrically similar to the downstream larger opening 4-5 and whose sides are widthwise divergent in a direction out wardy from the center of tubular core-element 35. Thus, there are provided a plurality of separate passageways 50 through stream-dividing members 40 which are adjacent to passageways 52. Each passageway 52 is formed by opposing outer sides 41 of adjacent stream-dividing members together with the arcuate portions 42 and tubular. core element 35 therebetween. The inlet end 53 of each of said passageways 52 also communicates with the inlet tube 22 and, in general, said passageway 52 is convergent rearwardly from the leading to the downstream edges thereof and is divergent widthwise, Thus in the construction shown in the drawings, which is an illustrative preferable embodiment of the invention, there are a plurality of radially disposed tubes 40 carried by tubular core element 35 to outlet tube 30 to define a plurality of separate and individually passageways 50 between each pair of which are reverse-shape passageways 52 for receiving the mix- 55 ture of hot gases and air in their passage through throat In accordance with my present invention, the hot gaseous discharge, which would normally discharge into the outer atmosphere from the opening at the tail end of the 0 housing 11, now discharge rearwardly against the cone 36 and into the rear end of the inlet tube 22 and simultaneously a plurality of streams of air between the H sup ports and the inlet tube 22 and housing 11 rush intothe discharge end of inlet tube 22 due to the injector action of the gaseous discharge stream from housing 11. As the hot gases discharge from the downstream end of housing 11 the mass of hot gases is spread at the center by the cone 36 to provide an annulus of hot discharge gases which are intermingled with the air which flows into the inlet tube 22 and acts as a cooling medium for the downstream end of housing 11. The hot gases intermingled with the. air from inlet tube 22 are cooled and in addition the. presence of air therein provides an oxidizing agent for supporting secondary combustion. The resultant mass is expanded upon reaching throat 32, and divided by stream-dividing member 40 into a plurality of adjacent streams through passageways 50 and 52 which alternate with each other.

1 In the course of passage of the mass of compressed and intermingled air and hot gaseous discharge into and through the passageways 50 and 52, the individual streams thereof are affected differently due to the reverse-shape of the passageways 50 compared with the shape of passageways 52. Because there is elfected a spreading of the hot gaseous discharge by the cone 36, an intermingling therewith of air admitted to the inlet tube 22, with expansion of the air and hot gases in its course of flow through a zone of gradually decreasing cross sectional area from the end of housing 11 to throat 32, and the subsequent fiow through the separate and individual passageways 50 and 52 ultimately into the outer atmosphere, there is an appreciable and significant suppression of jet noise which would be present in the absence of assembly 20, and also an appreciable increase in jet propulsion efliciency due at least in part to additional forward thrust imparted to plant 10.

I believe that the increase in efiiciency and additional forward thrust is due primarily to the spreading of the gaseous discharge by the cone 1%, with a resultant expansion of such discharge aided by the converging shape of the rear of the inlet tube 22 to throat 32, after which such gases, especially when further expanded and intermingled with the fast moving air which flows through inlet tube 22, pass into and through the individual passageways 50 and 52. As this air and discharge gaseous mass leaves throat 32, it enters the passageways 50 and expands and passes through said passageways whereby, due to a Venturi effect, a forward thrust is imparted to said plant in a direction opposite to the direction of flow of said air and gases into and through said throat. In the passage of the mass of mixed gases and air into and through passageways 52, due to the fact that the passageways 52 are different from passageways 50, that is the passageways of one set being divergent in the manner set forth and the other being of generally reverse-divergency, a further thrust is imparted to said combination. And in addition, the resultant mass as it discharges from the rear or downstream ends of the adjacent passageways 50 and 52, not only has been modified physically to vary the sound patterns therein due to the contour of the adjacent passageways, but, as they flow out of the downstream ends of these passageways the sound patterns thereat are further varied, all of which reduces the jet-noise. In addition, upon reaching the apron, which is disposed on the normally lower side when the airplane is in upright position in flight, these gases and air masses when intermingling with consequent change of sound pattern, just beyond the downstream termini of said passageways, :act to deflect and/or reflect and/or break up the sound column which might be formed, thereby aiding in reducing the jet-noise.

While the rear or downstream edge of that portion of outlet tube 30 which is spaced from the reflector or deflector apron 33 may be flush with the downstream edges of stream-dividing member 40, I prefer that it be disposed an appreciable distance forwardly of said edges of said stream-dividing member as shown in FIG. 5. By such construction, the discharge of the air and gaseous mass through passageways 52 which are not bounded by the reflector or deflector apron 33, and are at least half in number of the total number of all passageways 52, may be into the outer atmosphere at positions ahead or upstream of the discharge of the air and gaseous mass out of the tubes 50 of stream-dividing member 40, while through those passageways 52 bounded by the reflector or deflector apron 33 the discharge is in the same plane as that of passageways 50. If desired, the downstream edge of outlet tube 30 not bounded by the reflector or deflector apron 33 may have an internal narrow bead or flange (not shown), and in fact such bead may extend around the entire circumference of said outlet tube 30 even with the apron present to aid in providing a forward thrust upon discharge through passageways 50 and 52 into the outer atmosphere.

Since certain changes may be made in the -afore-described methods and constructions and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. The combination of a jet propulsion plant having an outer elongated housing of circular cross-section with a discharge mouth at its downstream end through which passes jet propulsion gaseous discharge therefrom, with a unitary noise suppression and thrust booster assembly coupled with said plant comprising a hollow funnel element including an upstream inlet tube surrounding the downstream end portion of said jet propulsion plant housing in radially spaced relation to provide a circumferential air admission passageway, and an outlet tube joined to and extending downstreamward from said inlet tube, and a gas deflection subassembly supported by the outlet tube interiorly thereof and including a tubular core element extending coaxially in said outlet tube in alignment with the axes of the inlet tube and the discharge mouth of the jet propulsion plan-t housing and extending upstreamward to the discharge mouth of the housing, the upstream end of said tubular core being closed and tapered to serve as a gaseous jet discharge spreader to deflect the discharge radially outward into the air stream issuing from the inlet tube, means in the outlet tube immediately downstreamward of the junction of the latter with the inlet tube to provide a constricted velocity accelerating throat, a plurality of radiating stream-dividing walls extending rearwardly of said constricted throat through the outlet tube in interconnecting relation to the latter and the tubular core to define passageways for receiving the mixture of gaseous discharge and air and dividing the same into separate substantially parallel streams.

2. The invention defined in claim 1, wherein the housing of the jet propulsion plant is rearwardly tapered externally to converge on the discharge mouth thereof, and wherein the inlet tube of the noise suppression and thrust booster assembly is rearwardly tapered internally to conform to the shape of said housing whereby the circumferential passageway therebetween directs incoming air convergingly inward to impinge upon the outwardly spread gaseous discharge.

3. The invention defined in claim 2, wherein the respective tapered external and internal surfaces of the housing and inlet tube are convexly curved axially.

4. The invention defined in claim 3, wherein the tapered upstream end of the tubular core element is convexly curved axially.

5. The invention defined in claim 1, wherein the tapered upstream end of the tubular core element is convexly curved axially.

6. The invention defined in claim 1, wherein the tapered upstream end of the tubular core element slightly penetrates the discharge mouth of the jet propulsion plant housing.

7. The invention defined in claim 1, wherein the housing of the jet propulsion plant is rearwardly tapered externally to converge on the discharge mouth thereof, and wherein the'inlet tube of the noise suppression and thrust booster assembly is rearwardly tapered internally to conform to the shape of said housing and merges smoothly and communicatingly with the constricted throat in the outlet tube.

8. The invention defined in claim 1., wherein the stream-dividing members located in the outlet tube of the noise suppression and thrust booster assembly are constituted by plural axially extending plates radiating from the tubular core element in circumferentially spaced relation to define mixture conducting passageways opening at their upstream ends into the constricted throat and at their downstream ends into the ouside atmosphere.

9. The invention defined in claim 8, wherein alternate mixture conducting passages are rearwardly expanding in cross-sectional area.

10. The invention defined in claim 9, wherein the walls that form the sides of each mixture conducting passage are radially outwardly diverging to provide passages of substantially tear-shaped cross-sectional configuration.

11. The invention defined in claim 10, wherein the side walls of alternating pairs of the stream-dividing members are interconnected contiguous to the outlet tube wall by arcuate radially outer Wall portions to form hollow mixture conducting tubes, wherein the rear ends of the said hollow mixture conducting tubes project rearward into the atmosphere beyond the trailing end of the outlet tube, and wherein the mixture conducting passageways intervening between said hollow tubes are rearwardly converging and discharge their streams of mixture into the fit 8v atmosphere in advance of discharge from the hollow tubes.

12. The invention defined in claim 11, to which is added a scoop-shaped rearwardly tapered apron of armate cross-sectional configuration extending rearward from the trailing edge of the outlet tube and merging with part of its circumference.

13. The invention defined in claim 12, wherein the apron is located in the underneath segment of the noise suppression and thrust booster assembly and extends through an arc of to to screen the ground underneath the jet propulsion plant from noise.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain May 16, 1951 

